Method of making twist drills



.Fufiy 1, 1924.

' 1,499, 797 N. E. VWOODS METHOD OF MAKING TWIST DRILLS Original Filed Sent. 50. 1919 2 Shee1.sShee't l if Z0001];

July 1 1924.

1,499,797 N; WOODS METHOD OF MAKING TWIST DRILIJS 2 Sheets-$heet 2 Originalfiled Sent. 30. 1919 37909141 oz Wbrmwli. Z00 a ti;

Patented July 1, 1924.

NORMAN E. WOODS, OF PATERSON, NEW JERSEY. I

METHOD OF MAKING TWIST DRILLS.

To all whom it may concern."

Be it known that I, NORMAN E. Woons, a citizen of the United States, residing at Paterson, in the county of Passaic and State of New Jersey, have invented new and useful Improvements in Mrthods of Making Twist Drills, of which the follow ing is a specification.

This invention relates to a new and improved method of making drills, particularly metal-boring drills of the twist type; and the present application is a division in part of my prior application filed September 80, 1919, Ser. No. 327,541, eventuating in Patent No. 1,384,788, dated July 12, 1921, covering a drill structure made in accordance with this method.

Drills of the twist type, as at present constructed, are defective in that each cutting lip cuts a single heavy chip, which chips, in addition to throwing heavy strain upon the drill, tend to lodge 'in the flutes and cause friction and loss of power. The

' packing of these chips in the fluts also tends to obstruct the flow of the lubricant to the cutters, with a further increase of friction, loss of power, and generation of heat and the burning and deterioration of the-metal of the drill at the point. More over, as the point has no cutting action, but acts merely to center the drill and force the metal beneath it from the center to ward the cutting lips, the drill, as it feeds into the work, causes a compression of the metal from the center toward the periphery of the drill. This compression greatly increases the weight of a chip from its normal weight under a fixed feed per revolution until it is compressed to a num-- ber of times its normal thickness of cut per revolution. Such compression is more perceptible, and adds still greater resistance to the progress of the drill, when lubricant does not meet the point and the chip is softened in heating up by the friction of the cutting edge and the chisel point. Hence the drill is liable to break underthe heavy strains and to become quicklydull,

"requiring frequent sharpening, and com paratively great power is required to feed the drill in its work. Drills providedwith flutes extending to points at their. heel edges also tend to further retardthe clearance of the chips and cannot be uniformly'tem-v Serial No. 483,886.

pered, owing to wide variations in the thlckness of the metal at different portions thereof.

Patent No. 1,384,738, dated July 12,

The general object of my invention is to provide a method of making a drill which overcomes the objections above noted to drills of ordinary construction, and which, therefore, is stronger and capable of resisting greater strains and is less liable to fracture than twist drills of the types in common use, andwhich will more efliciently lubricate the work and allow freer clearance of the chips and out faster with less resistance than any ordinary type of drill. ii

of a particular character for securing the desired results.

The invention consists of the features of construction, combination and arrangement of parts, hereinafter fully described and claimed, reference being had to the accompanying drawings, in which Figure 1 is a view in side elevation- 0f a blank from which the drill is made. Figure 2 is a cross-section through the blan Figure 8 is a View in side elevation twist drill embodying my invention.

Figure 4 is a plainview of the cutting end of the drill. 1

Figure 5 is a cross-section through the drill and an object being bored thereby.

Figure 6 is a diagrammatic plan View illustrating the cutting action of the. lips.

Figure 7 is a' diagrammatic view in elevation of the same.

Figure 8 is a view showing the division of the cuts and the chips formed by 'the cutting lips.

Figure 9 is a cross-section through a drill blank, showing a slight modification in the form of a groove. 7

Figure 10 is a similiar view of the drill ofa as formed from the blank shown in Figur I shank of the drill, which is of the ordinary twist form, 2 and 8 the portions of the body forming the spiral cutting blades, 4 the central web connecting the inner edges of the blades, 5 and 6 the flutes formed by and between the twisted blades, 7 the chisel cutting point at the outer end of the web, and 8 and 9 the cutting lips at the outer edges of the blades 2 and 3.

In carrying my invention into practice, I provide the face of each cutter blade 2 and 3 with a longitudinally eXtending channel or groove, the face of the blade 2 being provided with a groove or channel 10 and the face of the blade 3 with a groove or channel 11. These grooves or channels preferably extend throughout the length of the blades and intersect the cutting lips 8 and 9, thereby separating the respective cutting lips into a plurality ofcutting portions. As shown, the groove 10 separates the lip 8 into alined cutting portions 10 and 10 while the groove 11 separates the lip 9 into alined cutting portions 11 and 11 l-t will beobserved that the grooves lO'and 11 of the cutters are staggered with rela tion to each other, that is, arranged at different distances from the drill center, the lip 8 thus being separated by itsgroove 10 into a short straightinner cutting member 10 and relatively longer straight outer cutting inei'nber 10 while the lip 9,0n the contrary, is separated by its groove 11 into a relatively long s'traigh'tinner cutting member '11 and a relatively'shortstraight outer cutting member 11". Each cutting lip, therefore, instead of forming a chip coextensive in width therewith, produces a chip Whichis'divided into relatively narrow and Wider sections, both materially narrower than thewidth 'of the lip, leaving an uncut ridge of a depth corresponding to the groove therebetween. 'This is clearly shown in Figures 6, 7 and 8, wherein a, a anol'a respectively designate the chipsections'and' ridge formedby the cutting lip Sand Z), band b the'chip-sections and-ridge formed by the cutting lip 99. By the division of the chips in the manner stated the'objections incident to ordinary drills, in which each lip forms a single wide chip, are avoided, in that the sectional chip may be cut with greater freedom and ease and with a reduction of strain and friction, and the'sections of the chip havegreaterease of clearance, in that they will pass into and upwardly through the flutes in a free and easy manner, and withoutthe tendency to bind therein'a'nd create great resistance and friction, as with chips of normal size. Accordingly, the working strains upon the drill will be materially reduced and a drill of a given size, and rotated ata given speed, may be operated to cut atgreater speed than an ordinary drill and. with less driving power. Furthermore,

owing to the reduction of strain, the web 4 may be thinned or reduced in thickness by at least 15 less than the standard proportion, with the effect of narrowing the point 7, and without weakening the drill, with the additional advantageous result of diminishing to a great extent the compression of the chips by the point of the drill, friction and undue heating of the drill point and chips being also thus reduced to a further degree In practice, the grooves 10 and 11 of the cutters are preferably made deepest at the points where they intersect the lips 8 and 9 and then gradually diminishin depth toward the drill shank, and'the "groove'10 of one of the cutters, is preferably made of less depth than the groove, as the groove 11, of the other cutter, with the result of further reducing the sizes (widths) of the chips made by one cutter with respect to those made by the other, so that chips of different sizes will be formed which will more readily intermin'gle in their discharge to secure easy and rapid clearance. Another purpose of making the groove 11 deeper than the groove 10 is to allow greater clearance owing to its greater distance from the drill center and its greater ratio of cutting speed due to the larger circle in which it travels, also, bysuch clearance, to prevent burning of the cutting edge at the outer wall of sail groove 11 by high friction due to its speed. This deeper groove 11 also further promotes free "supply of lubricant to thecutting"surfaces. It will be understood that by thearran'gement of the grooves 10 and 11 in staggered relation, or at different distances from the center point 7, provision is made so that a cutting portion of each lip will remove the ridge left standing by the other lip, the cutting por tion 10 of the lip 8 removing the ridge 0 formed by the lip 9, while the cutting portion 11 of the lip 9 will remove'the ridge 6& formed by the lip 8, thus producing an absolutely smooth and finished bore. reducing the thickness ofthe web 4, it will further be evident that the depth of the flutes or clearance channels-5 and fi'will be increased, ensuring still further reduction of friction and any tendency of the chips to pack or bind therein. lt'will, of course, be'uuderstood that the grooves 10 and 11 also provide flow channels forthe passage of lubricant to the cutting surfaces.

The grooves may be forged during the process of'manufacture of cast in the drill in the process of making a cast drill, or may be milled or otherwise formed in a drill blank prior tothe operation'of twisting the same, my invention beingdirected toa form of groove resulting from the change produced by twisting of the drill blank from a groove ofprimarily different form. Fig ures l and 2 show a drill blank 1- having grooves 10 and 11' forged, cast or milled therein, from which blank the complete drill shown in Figures 3 to 8, inclusive, is made. As shown in Figure 2, the grooves 10* and 11 are primarily of half-round or semicircular form as made in the drill blank, and the result of twisting the drill blank to form the complete drill willbe to impart to each groove the semi-elliptical form or parabolically curved form shown in Figures 3. 4 and 5. This change in formation occurs, as stated, as a result of the twisting of the drill blank, and the result of the formation of a groove of semi-elliptical shape is to secure certain desirable and important advantages. Such form of the groove, which is deepest toward the periphery of the drill and shallowest at its side nearest the center of the drill, results in the formation of a groove which allows freer clearance of the chips and also of the production of an overhanging cutting edge or point 0 at the intersection of the wider end of the groove with the lip, which edge serves to make a clean cut and prevent any drag and the formation of any fins or ragged surfaces on'the chips liable to cause friction and retard the clearance of the chips. Also said cutting edge 10 tends to force the chips at right angles to the direction of rotation, thus centering them in the flutes and still further facilitating the clearance action.

11 Figures 9 and 10 I have shown a slight modification in the initial and final form of the grooves. By reference to Figure 9, it will be observed that while the groove 10 in the drill blanks is substantially of halfround form, like the groove 10 of Figure 2, the groove 11 of the drill blank in Figure 9 is much deeper, being substantially of semi-elliptical form with its major axis ar ranged at right angles to the cuttin edges of the drill. When this blank is twisted to produce the drill shown in Figure 10, the form of the shallow groove 10 is varied to accord substantially with the groove 11 of Figure 4, but the change in the form of the groove 11 is not so pronounced, said groove ll substantially preserving its original general U-shaped contour. However, owing to the twist of the drill, this groove 11* is given a change of shape, its major axis being varied from a straight line position at right angles to the cutting lips to a curved line position in which it is eccentric to the axis of the drill, thus giving the same cutting and clearance effect as the shallower grooves with a much deeper clearance. It will be observed that while in the two constructions shown the grooves differ initially in relative depth, the general shape of the grooves initially formed in the two blanks is the same, that is to say, that U- shaped grooves are provided, which may vary between a half-round and semi-elliptical form, with a corresponding change in the form of the grooves produced in the finished articles. 1

It will be obvious that, in addition to the functional advantages stated, the grooves 10 and 11 also serve to forma pilot or leader for the drill, which guides the drill or causes it to run more accurately or centrally than a drill of ordinary type.

While I have specified the use of a single groove in each drill lip, which is sufficient in drills up to a certain diameter, it is to be understood that any desired or required number of grooves may be formed in each drill lip as may be found most advantageous in drills of different diameters. Also while I have shown and described the use of grooves of certain form in the drill lips, I do not wish to be strictly confined thereto, except when specifically set forth in certain claims; as while such form of grooves has been found to be of desirable and special advantage, especially in their use in large drills which cut coarse chips, grooves of other equivalent form, when employed in connection with the other stated improvements of my invention, may be used in drills of small size which cut comparatively small chips. 1

In twist drills of ordinary construction the heel edges of the cutting members 2 and 3 generally extend to points or fiukes, with the result that the flutes 5 and 6 are con tracted thereby and the cutting members made of such irregular form and varying widths as to make it impossible to temper the drill evenly or in such manner to be free from flaws. I overcome this objection by rounding the heel ends of the cutting members, as indicated at 12, thus widenlngthe flutes 5 and 6 and removing an excess of metal adding to the difiiculty in tempering the drill evenly. By this construction an added advantage is obtained, in that in the upward fiow of the masses of chips through the flutes pockets or channels 12 are produced between the same and the surfaces 12, affording additional channels for the flow of lubricant to the cutting surfaces.

Having thus fully described my invention, I claim:

1. The method of making a twist drill which consists in providing a drill blank having grooves of a predetermined substantially circular cross-sectional form extending lengthwise of its blades and intersecting the cutting lips thereof, and then twisting the blank to impart the desired spiral form to the blades and to simultaneously distort the walls of the grooves so as to produce grooves which are comparatively shallow at their sides nearer to the center of the drill and increase gradually and progressively in width toward their sides farther from the center of the drill.

wise of the flutes of its blades and intersecting the cutting lips of the blades and then twisting the blank so as to impart the desired spiral form t the blades and simul taneously eiiect a resulting change in the shape of the grooves.

3. The. method of making; a twist drill each of the cutting'lips of WA ich isprovided with a plurality of cutting e ges, which consists in forming the blades of the drill before t ey are twisted with grooves of h ound form which extend through said c ring edges, and then bending the blades to the desired twist and simultaneously dis torting the grooves from half-round to resulting form.

4. The method of making a twist drill each of the cutting lips of which is provided with a plurality of cutting edges, which consists: in forming t-he'blades of the drill before they are twisted with U-shaped grooves which extend through said cutting edges, and then bending the blades to the desired twist and simultaneously distorting the grooves from U-shape to semi-elliptical form.

5. The method of making a twist drill each of the cutting lips of which is provided with a plurality of cutting edges, which consists in forming the blades of the drill before they are twistedwith grooves of halt-round form which extend through said cutting edges, and then bendingthe blades to the desired twist and simultaneously distorting the grooves from halfround to semi-elliptical form.

6. The method of making a twist drill each of the cutting lips of which is provided with a plurality of cutting edges,

which consists in providing a drill blank h .dinal grooves of liLfOl'H its time; and extending through their cnt ting edges, the groove of one flute being arranged at a greater distance troin the drill center than the groove of the other flute. and then twisting the blank to complete the drill and simultaneouslychange the form of each groove from. U-form to suostantially semi-elliptical form.

7. The method of making a twist vdri each of the cutting lips of which is 3,. c, vided with a plurality of cutting edges, which consists in providing a drill blank having longitudinal U-shaped grooves its flutes and intersecting iis cutting ed 'es, one of said grooves being deeper than the other and arranged at a greater distance from th drill centenand then twisting the blank to complete the drill and simultaneously change the shape of each groove from Udlorm to substantially semi-elliptical form.

8. The method of making a twist drill which consists in taking a" suitable drill blank having flutec bladesand forming the blades of the drill blank, before .saidblank is twisted, with longitudinal grooves of substantially 'U-shape in cross-section and intersecting the cutting lips of the blades, and then twisting the" drill blank so as to impart the desired spiral form to the blades and to simultaneously distort the grooves from a substantially -U-form to a form in which each groove is substantially semielliptical and shapedso as toproduce alt-its outer edge an inwardly projecting under cut cutter which overhangs'the deeper end of the groove.

In testimony whereof I aitix my signature.

NORMAN WDODS.

ti ll 

